The invention is based on a fuel injection pump for internal combustion engines. In a fuel injection pump of this type, the controlled fuel pressure of the interior controls both an adjustment of injection onset, with a shift toward early for cold starting, and a fuel injection quantity adaptation device.
For adjusting the injection onset at cold starting, or when the engine is not yet up to operating temperature, an increased fuel pressure is needed, which is operative in the work chamber and acts on the adjusting piston, and which effects a different shift of the injection onset toward early from that effected by the control of injection onset when the engine is at operating temperature. To attain this pressure, in the known pressure control valve a pressure chamber communicates continuously via a throttle with a restoring chamber, which in turn communicates via a relief line with a relief chamber. The pressure maintenance valve is disposed in the relief line and while the engine is still cold maintains a high pressure, regardless of the control device, while when the engine is at operating temperature the pressure maintenance valve is kept open by the control device. (Alternatively, a bypass could be opened instead as a function of temperature.) The pressure equilibrium occurring at the movable wall of the pressure control valve when the engine is cold keeps this valve in its closing position in which it estabblishes the desired high pressure. At the same time, however, this pressure acts on a spring-loaded adaptation piston, or adaptation device. This makes for an incorrect control of the fuel injection quantity; to overcome it, the pressure prevailing in the restoring chamber is fed to the back end of the adaptation piston, so that the resultant force of the spring moves the adaptation piston into its normal position. This fails to take into account the rise in rpm during engine warmup or the resulting demand for fuel, however.